The present application relates generally to mild hybrid powertrain controls and more particularly but not exclusively to controls for correction and/or compensation of motor/generator torque in mild hybrid systems. For future medium duty and heavy duty applications a variety of mild hybrid architectures are being considered. Mild hybrid architectures can take advantage of low cost components and minimize part proliferation varieties for multiple application and/or markets. In mild hybrid systems, devices such as electrical machines (e.g., motor/generators) and their associated power electronics (e.g., inverters and converters) are preferably robust, relatively high efficiency, and simple.
Controls for mild hybrid systems typically determine and send commands to control a motor/generator to provide torque to assist the engine in vehicle propulsion or receive torque to generate power for charging an energy storage system and/or powering electrical loads. Such commands typically depend, directly or indirectly, upon motor/generator torque determination which is influenced by current measurements associated with the energy storage system. Heretofore mild hybrid controls were believed to be effective to provide desired commands for motor/generator torque assist operation and generator operation. Surprisingly, the inventors have discovered that this is not always true. For example, it has now been realized that such controls may suffer from lower than desired current output during commanded torque assist operation. Such controls may further suffer from current reversal such that current to the energy storage system flows in a direction associated with power generation rather than torque assist which is desired. Such problems may arise at higher engine speeds or loads as well as at lower engine speeds or loads where neither power generation nor torque assist is desired. These unexpected problems create a number of undesired consequences including decreased efficiency, degradation of energy storage system function and life and substandard vehicle performance. These and other challenges with mild hybrid controls demonstrate that there remains a significant need for the unique apparatuses, methods and systems disclosed herein.